This invention relates to rounding edges on objects, and particularly to rounding edges on aerodynamic sliders for disc storage drives during manufacturing such sliders.
Sliders and sliders containing magnetic heads are typically manufactured by thin-film techniques such that several thousands of sliders or slider/head combinations are formed from a single substrate or wafer. The wafer is sliced into row bars, and each row bar is mounted to a mount bar by an adhesive. The row bar is lapped smooth to form an air bearing surface for each slider on the bar, and the slider features, including rails and transducing heads, are defined on the bars. The bars are then diced into individual sliders for subsequent assembly into disc drives.
Dicing is accomplished by cutting the bar at predetermined dice lanes between sliders using a diamond cutting blade. The dicing operation creates sharp edges at the junctions of the side surfaces with the other surfaces of the slider (i.e., the bottom, trailing, leading and top surfaces). Sharp edges might also be present at the junctions of the leading and trailing surfaces to the other surfaces due to the slicing operating forming the row bars. The bottom surface of the slider is either a substantially planar air-bearing surface or is a substantially planar nominal surface from which rails containing the air-bearing surface protrude. The sides are substantially planar surfaces that are normal to the bottom surface and to the leading and trailing surfaces; the side surfaces being formed by the diamond cutting blade when the bar is diced. The trailing surface ordinarily includes the transducing head features. The junctions of the various surfaces form 90xc2x0 edges of the slider. Additionally, sharp corners are formed at the junctions of any three of these surfaces.
These edges and corners, particularly those between the side and bottom surfaces and the trailing and leading surfaces, can damage the confronting data disc in the event of a head crash or other landings of the slider on the disc. Moreover, a risk exists that material from the slider will break loose from the edges and corners during operation of the disc drive, forming debris that adversely affects performance of the slider and/or the drive. The debris may collect in the rail structure of the slider, adversely affecting the flying characteristics of the slider. The debris might also collect on the disc, adversely affecting the smoothness of the disc surface, and hence the flying characteristics of the slider over the disc. The debris can also physically damage the read/write transducer, thereby adversely affecting the recording and readback characteristics of the disc drive. The risk that debris will break loose from the slider increases where the slider is constructed of a ceramic or other crystalline material. In such cases, less than 75%, and often less than 50%, of the facets of the microscopic crystals of slider material at the sharp edges and corners are bonded to adjacent crystals, resulting in weaker crystalline bonds at the edges and corners and increasing the risk that crystals will break off from the slider to form debris.
Numerous techniques have been employed to minimize the sharp edges and corners on sliders. One technique is to form chamfer across the edges and corners. However, a 45xc2x0 chamfer surface between the side and bottom surfaces will form sharp edges at the 45xc2x0 junction between the chamfer surface and each of the bottom and side surfaces. While the reduction of the angle at the edges due to the chamfer increases crystalline bond strength along the edges, thereby reducing the risk of material breaking off to form debris, the 45xc2x0 angle is still sharp enough that the risk of forming debris still exists. Consequently, there is a need to further reduce or eliminate edge angles.
Prior attempts to round the edges between the bottom surface and side surface have not been successful. More particularly, attempts at rounding the edges employed rounded cutting saws or wire saws. Misalignment of the saw to the edge of the slider resulted in imprecise cutting of the edges, usually resulting in one or both of the bottom and side surfaces being cut more deeply or more shallow than intended. As a result, sharp edges were created by the cutting process between the misaligned curved surface and the bottom and/or side surface. Additionally, the profile of the rounded edge was often concave, not convex. Also, wear of the saw resulted in inconsistent shapes of the rounded edges. Further, the rounded surface should have a small radius, usually less than about 15 microns, which is difficult to achieve with mechanical knives and saws.
There is a need for a technique of accurately forming a continuous curved edge surface in a slider such that the curved surface tangentially meets the side and bottom surfaces of a slider without the formation of sharp edges. The present invention provides a solution to this and other problems, and offers other advantages over the prior art.
One embodiment of the present invention is a process of forming a curved surface between first and second substantially planar and substantially normal surfaces on an object, such as a slider. A laser beam has a power distribution such that the laser power is greatest at the center of the beam and is weaker radially from the center of the beam. The laser beam is directed substantially normal to the first surface so that the center of the laser beam is contiguous the second surface. The laser beam is moved along a path substantially parallel to the second surface to ablate the object at the first surface adjacent the second surface. The power distribution provides peak power at the center of the beam, contiguous the second surface, with a power profile that decreases to the fringe of the distribution. Consequently, ablation of the material forms a continuous curved surface, generally in the shape of a cylinder, that extends between and tangential to at least one, and preferably both, the first and second surfaces.
In preferred embodiments, the power distribution is a Gaussian distribution whose power profile decreases substantially exponentially from the center of the beam to the fringe.
In some embodiments, the object includes a substantially planar third surface normal to the first and second surfaces. The laser beam is moved along a path parallel to the third surface to ablate the object adjacent the third surface to thereby form a second continuous curved surface between and tangential to the first and third surfaces.
In some embodiments, the object is a slider, characterized by a first continuously curved surface extending between and tangentially joined to the bottom and side surfaces and a second continuously curved surface between and tangentially joined to the bottom and trailing surface.
In yet other embodiments, a computer readable medium contains a computer readable program containing code that causes the computer to carry out the process of the invention.
Other features and benefits that characterize the present invention will be apparent upon reading the following detailed description and review of the associated drawings.